Such a mechanism is provided with a screw which comprises an outer thread, a nut which is arranged around the screw and which comprises an inner thread, and a plurality of longitudinal rollers which engage with the outer and inner threads of the screw and the nut. Compared with a ball screw mechanism, a roller screw mechanism has the main advantage of having higher permissible load capacities.
A first type of roller screw mechanism provides rollers which have an outer thread which is in engagement with the outer and inner threads of the screw and the nut, and which roll in the nut around the screw in a constant axial position. Such a mechanism is referred to as a satellite roller screw.
A second type of mechanism comprises rollers which are non-threaded but which are provided with grooves inside which the outer thread of the screw and the inner thread of the nut are accommodated. During a rotation of the screw or the nut, the rollers move axially in the nut. After a complete revolution, each roller is returned to the initial position thereof by cams which are fixed to the ends of the nut. Such a mechanism is referred to as a screw with roller recirculation.
In order to rotatably guide the screw of a roller screw mechanism and to support the loads transmitted, there is generally mounted an end bearing on a smooth portion of the screw. This bearing must support relatively high loads. Consequently, the end bearing generally used comprises four oblique-contact ball bearings which are accommodated inside a casing and preloaded axially by a self-locking clamping nut.
This solution has in particular the disadvantages of having a large axial dimension and requiring a large number of assembly operations. Furthermore, the weight of such a bearing is relatively great.
An object of the present invention is to overcome these drawbacks.